1. Field of the Invention
The present invention relates, in general, to planar motor driven positioning systems, and more particularly to such method and apparatus for positioning and aligning a wafer in a photolithographic system using a planar motor and isolating the system from the reaction forces of the planar motor.
2. Related Background Art
Various support and positioning structures are available for positioning an article for precision processing. For example in semiconductor manufacturing operations, a wafer is precisely positioned with respect to a photolithographic apparatus. In the past, planar motors have been advantageously utilized to position and align a wafer stage for exposure in the photolithographic apparatus. For example, U.S. Pat. Nos. 4,535,278 and 4,555,650 to Asakawa describe the use of planar motors in a semiconductor manufacturing apparatus.
A semiconductor device is typically produced by overlaying or superimposing a plurality of layers of circuit patterns on the wafer. The layers of circuit patterns must be precisely aligned. Several factors may cause alignment errors. Vibrations of the structures within the photolithographic system could cause misalignment of the wafer. The reaction forces between the moving portion and fixed portion of the planar motor are known to induce vibrations in the system.
As the semiconductor manufacturing industry continues to try to obtain increasingly tighter overlays due to smaller overlay budgets and finer conductor widths, the importance of alignment has been magnified. Precise alignment of the overlays is imperative for high resolution semiconductor manufacturing. It is therefore desirable to develop a means to reduce the effect of vibrations caused by the planar motor.